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This module introduces control flow in general and explains the use of the while loop in Python.

Table of contents

Preface

This module is one in a collection of modules on Python designed for teaching ITSE 1359 Introduction to Scripting Languages: Python at Austin Community College in Austin, TX.

What you have learned

Earlier modules in this collection have included instruction on the following topics:

  • numbers
  • variables
  • identifiers
  • strings
  • scripts
  • lists
  • tuples

This has prepared you to use Python as a very fancy desk calculator.

What you will learn

The next step in learning to program with Python is to learn how to apply repetition, modularity, and decision logic to your scripts. This is oftenreferred to in computer jargon as control flow .

This module introduces control flow in general and explains the use of the while loop in Python as an example of control flow .

Viewing tip

I recommend that you open another copy of this module in a separate browser window and use the following links to easily find and view the Figuresand the Listings while you are reading about them.

(Note to blind and visually impaired students: Most of the Figures and all of the Listings inthis module are presented in plain text format and should be accessible using an audio screen reader or a braille display. Note however that the requiredindentation may not be properly represented by an audio screen reader.)

Figures

  • Figure 1 . Output from the script in Listing 1.
  • Figure 2 . Output from the script in Listing 2.
  • Figure 3 . Visualization of the program.

Listings

  • Listing 1 . Typical script from earlier modules.
  • Listing 2 . Use a while loop to manipulate a list.

General background information

A typical script in the earlier modules looked something like the one shown in Listing 1 .

Listing 1 . Typical script from earlier modules.
# Illustrates extracting a # list element and extracting# elements from a nested list ##------------------------------- print("Create and print a list")listA = [100,200,300,400,500] print(listA)print("Original length is:") print(len(listA))print("Replace an element") listA[2]= [2,4,8,16,32,64] print("Print the modified list")print(listA) print("Modified length is:")print(len(listA)) print("Extract and display each")print(" element in the list") print(listA[0]) print(listA[1]) print(listA[2]) print(listA[3]) print(listA[4]) print("Extract and display each")print(" element in nested list") print(listA[2][0])print(listA[2][1]) print(listA[2][2])print(listA[2][3]) print(listA[2][4])print(listA[2][5])

The output produced by the script in Listing 1 is shown in Figure 1 .

Questions & Answers

A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
Aislinn Reply
cm
tijani
what is titration
John Reply
what is physics
Siyaka Reply
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Jude Reply
Can you compute that for me. Ty
Jude
what is the dimension formula of energy?
David Reply
what is viscosity?
David
what is inorganic
emma Reply
what is chemistry
Youesf Reply
what is inorganic
emma
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
Krampah Reply
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
Sahid Reply
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
Samuel Reply
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Joseph Reply
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
Ryan
what's motion
Maurice Reply
what are the types of wave
Maurice
answer
Magreth
progressive wave
Magreth
hello friend how are you
Muhammad Reply
fine, how about you?
Mohammed
hi
Mujahid
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
yasuo Reply
Who can show me the full solution in this problem?
Reofrir Reply
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Source:  OpenStax, Itse 1359 introduction to scripting languages: python. OpenStax CNX. Jan 22, 2016 Download for free at https://legacy.cnx.org/content/col11713/1.32
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